Apparatus for generating electrical energy by the application of heat



' Jan; 1967 T M. DICKINSON 3,299,299

APPARATUS FOR GENERATING ELECTRICAL ENERGY BY THE APPLICATION OF HEATOriginal Filed July 19, L961 2 Sheets-Sheet 1 CUEEI/W' by w d fill v1975 Attorney Jan. 17, 1967 T. M. DICKINSQN 3,299,299

. APPARATUS FOR GENERATING ELECTRICAL ENERGY BY THE APPLICATION OF HEATOriginal Filed July 19, 1961 2 Sheets-Sheet 2 (by 2} 4 W /7 /.'5Axrorney United States Patent 3,299,299 APPARATUS FOR GENERATINGELECTRICAL ENERGY BY THE APPLICATION OF HEAT Theodorer M. Dickinson,Schenectady, N.Y., assignor to I General Electric Company, a corporationof New York Continuation of application Ser. No. 125,196, July 19,

y 1961. This application Aug. 18, 1965, Ser. No. 483,013

13 Claims. (Cl. 310- 4) improved method and an apparatus for convertingthermal heat or other forms of energy directly into electrical energywithout the use of a rotating machinery.

This application is a continuation of copending application, nowabandoned, Serial No. 125,196, filed July 19, 1961, and assigned to thesame assignee as the present invention.

If a: conductive probe is inserted in an ionized plasma, itwill bebombarded with both positive ions and electrons. Ina normal plasma, thenumber densities of the electrons and positive ions are equal. Theelectrons are eitherat the same temperature as the ions or at a highertemperature, Because of their lighter mass, the velocities of theelectrons are higher and the number of electrons striking the probe perunit time exceeds the number of, positive ions striking the probe. If anelectrical circuit to the probe is completed, a net negative currentwillflow. If the probe is left open circuited, it will charge up to anegative potential relative to the plasma such that the resulting,electrostatic force on the electrons repels all but the most energeticelectrons, reducing the flow of electrons to. a value exactly equal tothat of the positive ions, and resulting in a net current equal to zero;The magnitude of the negative potential so pro duced depends on thetemperature of the electrons; the

higher. their temperature, the higher the negative potential; Thenegative potential may be expressed by the equation where T and T arethe electron and ion temperatures in degrees Kelvin and, m and m theirrespective masses. Ifa second probe is inserted in the plasma at a pointwhere the electron temperature is different from that at thefirst probe,the second probe will charge up to a different 1 potential and apotential difierence will exist be- I tween the two probes. If a load isconnected between the two probes, current will flow therethrough andelectrical. power may be extracted from the plasma. The energy which issupplied to the plasma to maintain it in an ionized state is thusconverted directly to electrical energy, with the plasma acting as thecoupling medium.

Heretofore, the potential difference between the two electrodes hasbeenachieved by utilizing electrodes of different shapes or, of differentmaterials or operating at diiferent temperatures; or by other methods,such as the use of magnetic fields or electron attachment to theneutralgas atoms to reduce the electron flow to one electrode relative to theother. For the embodiment of the present invention, it is only necessarythat the electron temperature be higher at one electrode than at theother. Therefore, a principal object of the present invention is toprovide an improved energy converter for converting heat or other formsof energy directly into electrical energy.

3,299,299 Patented Jan. 17, 1967 A further object of the presentinvention is to provide both an improved method and. apparatus forutilizing the differential rates of diffusion of charged particles of anionized medium to achieve a source of electrical power.

Briefly, in one form of the present invention, energy in a first formsuch as heat, nuclear radiation, or electromagnetic energy is converteddirectly into energy of a second form, i.e., electrical energy. This isaccomplished by producing a gradient in the temperature of the electronsin an ionized plasma without regard to the material, shape or any othercharacteristic of the electrodes immersed in the ionized plasma.

FIGURE 1 is a schematic diagram of an energy converter containing anionized plasma;

FIGURE 2 is a graph showing the electrical characteristics for theelectrodes of the energy converter shown by FIGURE 1;

FIGURE 3 shows an embodiment of the energy converter shown in FIGURE 1;

FIGURES 4a and 4b illustrate modifications of the converter shown inFIGURE 3;

FIGURE 5 shows a plurality of the energy converters of FIGURE 3 arrangedto form a typical system; and

FIGURE 6 illustrates an alternate embodiment of the present invention.

The operation of one embodiment of the present invention may best beunderstood by reference to FIGURE 1 of the drawings which illustratesschematically a chamher 1 containing an ionized plasma 2. Ionization ofthe plasma is maintained by some means such as an external source ofenergy in the form of ionizing radiation 3. It would also be possible toapply a nuclear energy source or source of another type internally.Immersed in the ionized plasma are two electrodes 4 and 5 which float atdiiferent potentials. As no special design requirement exists for theseelectrodes, they may be of tungsten or any other material having similarthermal and electrical conductivity properties. If a circuit isconnected between the two electrodes 4 and 5, current flows when inaccordance with the invention there is created a gradient in thetemperature of the electrons of the plasma between the electrodes. It isonly necessary that the temperature of the electrons be greater near oneelectrode than the other. In FIGURE 1, it can be seen that electrode 4is in the region of higher electron temperature due to the fact that theionizing radiation is directed toward the plasma in that area adjacentto the electrode 4. Since the radiation is concentrated in the plasmanearer electrode 4, the electron current fiow from the plasma to thatelectrode will exceed that from the plasmato electrode 5 and a net flowof electrons externally from electrode 4 to electrode 5 will result.Thus, the gradient in temperature of the electrons existing in theplasma between the electrodes produces a flow of current.

FIGURE 2 is a graph of the characteristics of the electrodes 4 and 5.Since the temperature of the electrons in the region of electrode 4 ishigher than that at electrode 5, its floating potential (A of electrode4 is more negative than that of electrode 5 shown as (B A high impedancevoltmeter connected between the electrodes reads this potentialdifference. If the electrodes are connected together through a lowimpedance ammeter, the potential of electrode 4 will become lessnegative and that of electrode 5 more negative, until equal currents areattained. The new potential of the two electrodes is indicated by thevertical dashed line connecting points of equalcurrents on the twocurves (A and (B If a resistive load 6, in FIGURE 1, is connectedbetween the two electrodes 4 and 5, and a line is drawn on the plothaving a negative slope equal to twice the value of the resistance andintersecting the two curve points at equal 3 currents as at (AL) and(BL) then the voltage across the load will be shown as E and the currentI Therefore, the powerproduced is E I Thus efiectively there has been aconversion of nuclear energy or electromagnetic energy into electricalpower.

In FIGURE 3 is shown one embodiment of the energy converterdiagrammatically shown by FIGURE 1. The device may comprise a cell 11 inwhich an inner cylinder 7 constitutes one electrode and anotherconcentric outer cylinder 8 the other electrode. End walls of thecylindrical structure are provided although not shown in FIGURE 3; andthese walls are formed of electrical insulating material. Within theinner cylinder 7 may be placed a fissionable material 9 such as U U orPu The space between the two cylinders is filled with a gas 10' of lowionization potential, such as cesium at atmospheric or higher pressure,or of another easily ionized gas. Ionization radiation from thefissionable material 9' passes through the thin walls of the innercylinder 7 to ionize the plasma and heat the electrons near the innercylinder to a temperature greater than those near the outer cylinder,there-by establishing the temperature gradient required to produce ad'iiference in potential between the inner and outer cylinders. Theplasma near the inner electrode 7 may operate at 3,000 K. to produce anappreciable amount of thermal ionization of the vapor. This may beaugmented to some extent 'by ionization resulting directly from the highnuclear radiation intensity Within the cell. At the assumed temperature3,000 K. and at one atmosphere pressure, cesium is thermally ionized toabout one part in 140, representing an ion density of l.73 10 ion/cm.These ions diffuse through the gas and are cooled down by collision. Ifno recombination occurs during their transit to the outer electrode 8,the saturation current density to the outer electrode 8 is approximatelyamps/om. or 190- amps./cm. of length of the cell shown by FIGURE 3. Thetemperature gradient in the cesium vapor will produce a no loadpotential difference of 1.44 volts between the two electrodes 7 and 8because of the plasma between the electrodes operating at 3,000 K. andapproximately 300 K. respectively near the inner 7 and outer 8electrodes. If an optimum value of load is selected, the maximum outputof this one cell is obtained with 184 amps. and 1.23 volts resulting inan output of 226 watts/ cm. of length. Under high temperatureconditions, thermal electrons will be emitted (from the solid surfacesof the electrodes. If the work function is low enough and thetemperature high enough, this emitted electron current, which is inopposition to the electron current coming from the plasma, willappreciably reduce the output. One method of overcoming this deficiencyis by the use of an additional electrode, or plurality of electrodes,positioned in the region of high electron temperature, but cooled byappropriate means to a temperature at which the current due to thethermionic emission of electrons from the electrodes is relatively smallwith respect to the current due to the flow of electrons from the plasmato the electrodes. Embodiments showing this configuration are shown inFIGURES 4a and 4b. The elements numbered 7 to 11 are the same as shownin FIGURE 3. In FIGURE 4a, the central core 7 containing a fissionablematerial 9 is surrounded by a grid of water-cooled tubes 12 which servesas the negative electrode. In FIGURE 4b, the water-cooled negativeelectrode 12 is centrally located at the highest temperature point inthe chamber and is surrounded by a cluster of tubes 7 containingfissionable material 9. When these configurations are utilized, the load6 is connected to the cooled electrode or electrodes 12 and the innercylinder or cylinders 7, previously connected to the load, and used aselectrodes, are now used only as containers in which the means forsupplying the heat energy is disposed.

There may be losses in the cells resulting from heat transfer from theplasma near the inner electrodes 7 to the outer electrode 8. This heattransfer may be produced by several means including radiation,conduction by a neutral gas, release of ionization energy, and kineticenergy of ions arriving at the outer electrode 8. Because of thecylindrical geometry of the cell, the heat radiated from the innerelectrode 7 is partly reflected and the thermal loss is determined bythe absorptivity of the outer electrode 8. With a polished surface theheat loss by the absorptivity of the outer electrode 8 may be kept low.If, for purposes of this example, a 10% absorptivity is assumed for theouter electrode 8 and 50% emissivity for the inner electrode 7, then theheat loss at 3,000 K. is 20 watts/cm. or 126 watts/ cm. length.Conduction heat loss is 11 watts/cm. length. The ionization energy willbe 3.87 volts and the kinetic energy will be 0.16 volt so that with 180amps/cm. length, the loss from these two sources will be 742 watts/cm.of length. The net efiiciency is then output/ (loss-l-output) which isFIGURE 5 shows an arrangement in which the cells are stacked to form adevice which is designed primarily as an electrical generator. In theexample shown, since the cells have a five centimeter center to centerspacing, the arrangement allows for 400 cells per square meter or 900kilowatts per centimeter of length. Therefore, in one cubic meter of thedevice there may be generated 9 megawatts of electrical power with 36megawatts of heat loss. If desired, a coolant and moderator such aswater may be circulated between the cells of the device in order toimprove the efiiciency of the operation.

Though a prefered practical embodiment of the invention has beendescribed above, it is well to note that instead of using a fissionreaction at the inner electrodes 7 to produce heat, uranium vapor may besubstituted for the cesium and allowed to react. Since the uranium hasan ionization potential of 4 volts, it is thermally ionized in almostthe same percentage, at the same temperature, as cesium. In such anarrangement the temperature of the gas may be permitted to react tohigher values to produce higher cell voltages and resulting higherefliciencies.

Another form of the cell described using an easily ionized gas such ascesium vapor may utilize a solar energy to heat the inner electrodesrather than a radioactive material such as U In addition other types ofheat, such as flue gases from power plants, atomic installations orblast furnaces or from the exhausts of jet engines and rocket missilesmay be used. In the case of waste heat from jet engines and rocketmissiles, such an apparatus may be used to operate the electricalequipment of the device from which the waste heat is obtained. However,regardless of the heat source utilized or the type of materials used forthe electrodes, which as previously mentioned may be tungsten or anymaterial having similar thermal and electrical conductivity properties,the thermal gradient in the ionized plasma between the two electrodesproduces the net potential difference and thereby generates electricitydirectly from another source of energy.

An embodiment of the present invention which utilizes electromagneticradiation is shown schematically in FIG- URE 6. The device may comprisea cylindrical cell 13 in which an outer cylinder 14 serves as oneelectrode and an inner centrally disposed cylinder 15 the otherelectrode. End walls 16 enclose an ionizable gas 17 such as cesium,mercury vapor, argon, or the like. Electromagnetic energy is collectedby a suitable device such as an antenna 19 connected to the innerelectrode 15 by means of a lead 22. The electromagnetic energy in theform of a high frequency alternating current passes through the cellfrom the inner electrode 15 to the outer cylinder 14- ionizing the gas.If the electrical impedance of the cell is properly matched, such as byproper choice of dimensions and gas pressure, to the rest of thecircuit, a large percentage of the electromagnetic power received isabsorbed in the plasma, raising its temperature and producingionization.

With the cylindrical geometry chosen, the electric field will bestrongest at the central electrode. Since power is absorbed in theplasma by coupling through the elec/ trons, the electrons in thevicinity of the central electrode will have the highest temperature.This creates the required gradient in the electron temperature toproduce a potential difference between the inner and outer cylinders inthe same manner as in the embodiment shown in FIGURE 3. Ifa load isconnected between the inner and outer cylinders, a negative currentflows out of the inner. cylinderdelivering .electn'calpower to the load.To preventthe high frequency alternating current from passing throughthe load,and thus reducing the current flowing in. the desired paththrough the cell, a choke coil 20 or other device having a highimpedance to high frequency current but having :a low impedance to theload the load to. the cell as is shown in FIGURE 6.

Becausethet ionization which is produced in the cell as described.doesnot .dec'ay instantly, and although the high. frequency alternatingcurrent may be of sinusoidal form passing through zero twice each cycle,the ionization tends to persist during the period when the highfrequency alternating current passes through zero, and theunidirectional current through the load is nearly constant at avaluewdetermined by the magnitude of the high frequency current. If themagnitude of the high frequency current varies slowly, the ionizationlevel and the load current will vary in a like manner. By proper choiceof dimensions of the cell and type of gas mixture used, the ionizationlevel can be made to follow more rapid changes in the. magnitude of thehigh frequency current. Underthese conditions, the electromagneticradiation can be modulated at a commercial power frequency with theresult being that the current supplied to the load will vary fromzero tomaximum at the commercial power frequency rate. By using a filter ortransformer to couple to. a load, the direct current component can beremoved leaving a pure alternating current. This principle may also beextended to audio or higher frequencies if desired. In FIGURE 6, thecollector for the electromagnetic radi ation is shown connected to thecell by means of a single lead 22. if Conventional coaxial conductors orwave guides may; also be used to deliver the electromagnetic energy tothe cell.

Although particular embodiments of the present invention have beendescribed, many modifications may be made and it is understood to be theintention of the appended claims to cover all such modifications as fallwithin the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Apparatus for converting energy in a first form into electricalenergy comprising:

(a) an enclosure,

(b) an ionizable gaseous medium within said enclosure, said mediumconstituting the primary source of electrons,

(c) means for ionizing said gaseous medium,

(d) a first electrode in contact with said medium and subject tobombardment by both positive ions and electrons from said medium,

(e) a second electrode in contact with said medium and spaced from saidfirst electrode, said second electrode also subject to bombardment byboth positive ions and electrons from said medium,

(f) means for producing a thermal gradient in said medium between saidspaced electrodes, said thermal gradient causing a greater number ofelectrons and positive ions to strike one of said electrodes than theother of said electrodes so that a potential differ ence is establishedtherebetween, and

(g) means for utilizing said potential difference.

2. An. apparatus for converting energy as described in claim 1 whereinsaid ionizing means and said means current'is inserted in series withthe lead 21 connecting" for producing a thermal gradient are locatednearer one of said electrodes than the other of said electrodes.

3. An apparatus for converting energy as described in claim 1 whereinsaid first electrode comprises said enclosure and said second electrodeis cooled in order to produce the thermal gradient.

4. An apparatus for converting energy as described in claim 1 whereinsaid ionizing means comprises radiation means.

5. An apparatus for converting energy as described in claim 1 whereinsaid ionizing means comprises a high frequency electric field.

6. An apparatus for converting energy as described in claim 5 furtherincluding means for modulating said high frequency electric field toproduce a lower frequency voltage for said utilizing'means.

7. An apparatus for converting energy as described in claim 1, whereinsaid first probe comprises an inner cylinder, said second probecomprises an outer concentric cylinder, said outer concentric cylinderalso comprising said enclosure, and said thermal gradient producing andionizing meansare disposed within said inner cylinder.

8. Apparatus for converting energy in a first form into electricalenergy comprising:

(a) an enclosure,

(b) an ionizable gaseous medium within said enclosure, said mediumconstituting the primary source of electrons,

(c) means for ionizing said gaseous medium,

(d) a first electrode in contact with said medium and subject tobombardment by both positive ions and electrons from said medium, saidfirst electrode also comprising said enclosure,

(e) a container centrally disposed within said enclosure,

(f) a plurality of second electrodes, said plurality of electrodes beingdisposed about said container and being subject to bombardment by bothpositive ions and electrons from said medium,

(g) means for producing a thermal gradient in said medium between saidfirst and said second electrodes, said ionizing means and said thermalgradient producing means being disposed within said container, saidthermal gradient causing a greater number of electrons and positive ionsto strike one of said electrodes than the other of said electrodes sothat a potential difference is established therebetween, and

(h) means for utilizing said potential difference.

9. Apparatus for converting energy as described in claim 8 wherein saidplurality of second electrodes are cooled in order to further aid insetting up the thermal gradient in said medium.

10. Apparatus for converting energy as described in claim 9 wherein saidplurality of cooled electrodes comprise hollow cylindrical membersthrough which water passes.

11. Apparatus for converting energy of a first form into electricalenergy comprising:

(a) an enclosure,

(b) an ionizable gaseous medium within said enclosure, said mediumconstituting the primary source of electrons,

(c) means for ionizing said gaseous medium,

((1) a first electrode in contact with said medium and subject tobombardment by both positive ions and electrons from said medium, saidfirst electrode also comprising said enclosure,

(e) a second electrode in contact with said medium and spaced from saidfirst electrode, said second electrode also subject to bombardment byboth positive ions and electrons from said medium, said second electrodebeing centrally disposed within said enclosure,

(f) a plurality of containers disposed between said first and saidsecond electrodes,

(g) means for producing a thermal gradient in said medium, said thermalgradient causing a greater number of electrons and positive ions tostrike one of said electrodes than the other of said electrodes so thata potential difierence is established therebetween, said thermalgradient producing means and said ionizing means being disposed in saidplurality of containers, and

(h) means for utilizing said potential difference.

12. Apparatus as described in claim 11 wherein said second electrode iscooled in order to further aid in setting up the thermal gradient insaid medium.

13. A device for generating electrical enegy comprismg:

(a) a plurality of cells in stacked arrangement, each of said cellscomprising an inner cylindrical tungsten electrode and an outerconcentric cylindrical tungsten electrode, said outer tungsten electrodealso comprising an enclosure for said generator,

(b) an ionizable cesium vapor contained between said electrodes, saidvapor constituting a primary source of electrons, V

(c) a core of U-235 within said inner electrode for difference isestablished therebetween, and (d) means for connecting a load to saiddevicev to utilize the potential difference developed by said cells.

References Cited by the Examiner UNITED STATES PATENTS 2,598,925 6/1952Linder 3104 X 2,718,786 9/1955 Ohmart 3104 X 2,754,442 7/1956 Bontry310-4 X 2,817,776 12/1957 Cohen 310-4 X 2,837,666 6/1958 Linder 3104 X2,980,819 4/1961 Feaster 3104 3,021,472 2/ 1962 Hernquist 310-4 X3,113,091 12/1963 Rasor 3104 X MILTON O. HIRSHFIELD, Primary Examiner.J. W. GIBBS, Assistant Examiner.

1. APPARATUS FOR CONVERTING ENERGY IN A FIRST FORM INTO ELECTRICALENERGY COMPRISING: (A) AN ENCLOSURE, (B) AN IONIZABLE GASEOUS MEDIUMWITHIN SAID ENCLOSURE, SAID MEDIUM CONSTITUTING THE PRIMARY SOURCE OFELECTRONS, (C) MEANS FOR IONIZING SAID GASEOUS MEDIUM, (D) A FIRSTELECTRODE IN CONTACT WITH SAID MEDIUM AND SUBJECT TO BOMBARDMENT BY BOTHPOSITIVE IONS AND ELECTRONS FROM SAID MEDIUM, (E) A SECOND ELECTRODE INCONTACT WITH SAID MEDIUM AND SPACED FROM SAID FIRST ELECTRODE, SAIDSECOND ELECTRODE ALSO SUBJECT TO BOMBARDMENT BY BOTH POSITIVE IONS ANDELECTRONS FROM SAID MEDIUM, (F) MEANS FOR PRODUCING A THERMAL GRADIENTIN SAID MEDIUM BETWEEN SAID SPACED ELECTRODES, SAID THERMAL GRADIENTCAUSING A GREATER NUMBER OF ELECTRONS AND POSITIVE IONS TO STRIKE ONE OFSAID ELECTRONS AND THE OTHER OF SAID ELECTRODES SO THAT A POTENTIALDIFFERENCE IS ESTABLISHED THEREBETWEEN, AND (G) MEANS FOR UTILIZING SAIDPOTENTIAL DIFFERENCE.